A cylinder of an internal combustion engine may be supplied with fuel via port fuel injectors and direct fuel injectors. By providing the cylinders fuel via two types of fuel injectors, each type of fuel injector having different advantages, it may be possible to operate the engine at higher power levels and with reduced emissions. Nevertheless, it may be difficult to control the engine's air-fuel ratio during transient operating conditions because a desired torque and/or an amount of air entering the cylinder while fuel is being injected to the cylinder may vary. Fueling the engine accurately at higher engine speeds becomes even more difficult because there is less time between cylinder events at higher engine speed.
The inventors herein have recognized the above-mentioned challenges and have developed an engine fueling method, comprising: port injecting fuel to a cylinder in a cylinder cycle via a first fuel pulse width, the first fuel pulse width not adjusted responsive to engine operating conditions after being scheduled for delivery; and directly injecting fuel to the cylinder in the cylinder cycle via a second fuel pulse width, the second fuel pulse width selectively adjusted after being scheduled for delivery.
By estimating a desired torque or cylinder air charge before air is inducted into a cylinder and port injecting an amount of fuel based on the desired torque or cylinder air charge without updating the port injected fuel amount during a cylinder cycle, it may be possible to provide the technical result of determining an amount of direct fuel to be injected to the cylinder with full knowledge of the amount of port injected fuel, even before injection of the port injected fuel is complete. The port injected fuel amount may then be subtracted from a desired cylinder fuel amount to determine the amount of fuel to directly inject to the cylinder for a combustion event where both the port injected fuel and the direct injected fuel are combusted. Consequently, it may be possible to provide masses of port and direct injected fuel that match a desired mass of fuel for a cylinder. Additionally, since the direct injected fuel may be injected during an intake stoke and compression stroke of the cylinder, the amount of direct injected fuel may be revised during the cylinder cycle to improve accuracy in the amount of fuel delivered during the cylinder cycle. Therefore, engine air-fuel control may be improved, even at higher engine speeds.
The present description may provide several advantages. Specifically, the approach may improve engine air-fuel ratio control. Additionally, the approach may provide for increased amounts of engine torque as compared to when fuel is injected via only a single fuel injector. Further, the approach provides a procedure to reduce the possibility of fuel entering a cylinder during a cylinder cycle for which the fuel was not intended.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.